Clean, wash and drain the lamb's lettuce well. Wash the grapes, dab dry, cut in half and remove seeds. Fry slices of bacon in a pan until crispy brown. Remove and let cool.
Add vinegar, oil, salt and pepper to the hot pan and toss briefly. Set aside. Mix lamb's lettuce and grapes loosely and divide into four plates. Crumble the crispy bacon slices and sprinkle over the salad.
Pour the lukewarm vinaigrette over it.